Power supply circuits for supplying a power to each electronic component mounted onto a printed circuit board are integrated into one portion near the edge of the circuit board in many cases. Such a power supply circuit decreases a relatively high voltage supplied from the outside of the board down to a low voltage for each electronic component (each device) and applies the voltage to each electronic component. However, in recent years, a voltage for each electronic component mounted onto the circuit board tends to decrease, while a current value for each electronic component tends to increase. Under the above circumstances, such a system as supplies a current to each electronic component in a concentrated manner from power supply circuits integrated at one portion on the board has a problem that a circuit length to supply a current from the power supply circuit to each electronic component is increased and a voltage is lowered on its way to the component.
As a main countermeasure against the problem is adopted a distributed current supplying system where a compact, high-speed-response power supply is provided near each of components on the circuit board, which require a power. According to such a distributed current supplying system, although a current path up to the compact power supply circuit on the board is long, a current value of a current flowing therethrough is high, so an influence of voltage drop is small. Further, a current path of a low voltage that is reduced at the compact power supply circuit, up to each electronic component can be shortened. Thus, an influence of voltage drop on the path of a current supplied from each power supply circuit to each electronic component in the circuit, can be suppressed.
Moreover, a recent tendency is to downsize a circuit board along with reduction in product size and yet, to increase the number of electronic components mounted onto the circuit board. The circuit board is proceeding toward compact/high-density mounting. Following this tendency, a method of mounting electronic components onto a so-called mother board and mounting a power supply circuit is mounted onto a so-called daughter board to connect these boards with an electrical connector, is generally employed.
Even in the case of using the mother board and the daughter board, it is possible to integrate power supply circuit to one portion on the daughter board and supply a power from the daughter board to each electronic component on the mother board by the use of a connector including many pins. However, this configuration involves the aforementioned problem of voltage drop. To that end, a distributed power supply system is adopted; in the system, power supply circuit 2 are distributed on a daughter board 1 in accordance with positions of electronic components 5 arranged on a mother board 4, and a power is supplied from each power supply circuit 2 to the mother board 4 using many connectors 3 as illustrated in FIGS. 1A and 1B.
The above distributed power supply system where the power supply circuit 2 are distributed on the daughter board 1 and a power is supplied from each power supply circuit 2 to the electronic components 5 on the mother board 4 using many connectors 3, follows the rule that the power supply circuits 2 may provide near the electronic components 5. However, in this example, plural connectors 3 are used, which causes a problem that plural connectors 3 may not be fitted properly due to mounting tolerances of the plural connectors 3, and if forcedly fitted, the connectors 3 cause any defect.
A detailed description thereof is given with reference to FIGS. 2A and 2B. To precisely fit the connectors 3 provided on each of the mother board 4 and the daughter board 1, coordinates of the connector 3 on the mother board 4 and coordinates of the connector 3 on the daughter board 1 should match each other when the boards are bonded. FIGS. 2A and 2B illustrate coordinates of the connector 3 on the mother board 4 and coordinates of the connector 3 on the daughter board 1. The respective coordinates involve tolerance. Provided that the lower right position of each board in the figures is set as the origin, the coordinates of the connector 3 on the mother board 4 is expressed by (Xm1±α, Ym1±α). The tolerance ±α is a combination of tolerance ±A involved in pattern formation on the board and tolerance ±B involved in arrangement of the connectors 3 on the pattern. More specifically, tolerance ±α=(±A±B). Further, the shape of the board 4 also has the tolerance ±β.
The tolerances are each on the order of 0.1 mm. However, at the worst, the plural connectors 3 involve the sum of the maximum values of the tolerances. Accordingly, in such cases, the plural connectors 3 mounted to the mother board 4 and the daughter board 1 cannot be engaged properly only by adjusting positions of the mother board 4 and the daughter board 1.
To overcome the problem, prior art disclose a movable connector that can be moved relative to the other connector when fitted thereto. A movable connector disclosed in FIGS. 2 and 6 of Japanese Laid-open Patent Publication No. 2002-329556 includes a stationary housing and a movable housing, and the movable housing can be moved within a movable range of a spring of the stationary housing. Electric connection between a circuit pattern on a circuit board and the connector is established by pressing the connector to the circuit pattern by utilizing spring property of a connecting terminal (contact) provided at the bottom of the movable housing.
Further, an electrical connector disclosed in Japanese Laid-open Patent Publication No. 2005-166302 (FIGS. 3 to 5) is structured such that a sliding mechanism is provided to a stationary member and a housing on a circuit board to allow the connector to move only in a horizontal direction. Further, an electrical connector disclosed in Japanese Laid-open Patent Publication No. 2005-005096 (FIGS. 8 to 16) includes a connector plug and a connector socket composed of a stationary portion and a movable portion. The stationary portion of the connector plug has projections at four positions. By inserting the projections to holes formed in the movable portion, the stationary portion and the movable portion can be assembled. A space between the outer edge of the stationary portion and the inner edge of the movable portion is a movable range of the movable portion. A terminal of the movable portion is set wide so as to establish electrical connection with the stationary portion. Further, a terminal of the stationary portion protrudes downwardly before assembly to maintain electrical connection to the stationary portion even if being moved after assembly.
However, the movable connector as disclosed in the Japanese Laid-open Patent Publication No. 2002-329556 includes many contacts, which are thin and long due to spring property thereof and have a high electric resistance, resulting in a problem that the connector is inappropriate to supply a large current. Further, the electrical connector as disclosed in the Japanese Laid-open Patent Publication No. 2005-166302 also includes many contacts and is not intended to absorb various tolerances of the upper and lower boards upon engagement, resulting in a problem that the connector is inappropriate to connect the upper and lower boards with plural connectors. Further, the electrical connector as disclosed in the Japanese Laid-open Patent Publication No. 2005-005096 is intended to connect printed boards together but its terminal is thin and long and has a high electrical resistance similar to the Japanese Laid-open Patent Publication No. 2002-329556, resulting in a problem that the connector is inappropriate to supply a large current.